This invention relates to a moving picture processing device for processing a moving picture containing a redundant picture. More particularly, it relates to a moving picture processing device for processing moving picture signals obtained as a result of photo-electric conversion of a source of original pictures, such as a motion picture film.
For interconnecting plural devices handling moving pictures in a moving picture processing system, it is necessary to synchronize the moving pictures. In general, one of the devices of the system is used as a reference and the remaining devices are caused to follow the reference device. This reference device is termed a master and the remaining devices are termed slave devices. The master device is exemplified by a video camera, a VTR, a video disc or a computer, as a supply source for moving pictures, while the slave device is exemplified by an encoder, a VTR or a monitor designed to process the moving pictures.
The synchronization signal from the master device is supplied as a reference clock for a phase locked loop (PLL) of the system.
An illustrative moving picture encoding system is shown in FIG. 1.
This moving picture encoding system has many clock signals, such as clock signals for an encoder 101, clock signals for a local decoder 102, or display clock signals. Of these, a picture synchronization input S2, supplied from a digital VTR 100 of a picture input device 10, as a supply source for the moving pictures, represent master clock signals.
The encoding of the moving pictures is a technique recognized to be indispensable for reducing transmission costs at the time of digital transmission of moving pictures.
For example, a picture processor 20 is made up of the encoder 101 and the local decoder 102, and implements a hybrid encoding method consisting in the combination of motion compensation prediction and DCT well-known as MPEG 2 (ISO/IEC 13813-2).
An input picture S1 is given at a rate of 30 frames/second (60 fields/second) or 25 frames/second (50 fields/second).
In FIG. 2, the fields shown by intersected hatching denote top fields or odd fields, while the fields shown by hatching denote bottom fields or even fields. In the present example, each frame is necessarily constituted by a pair of fields. Thus a frame synchronization signal S2 is supplied in synchronism with each frame. In this case, all input pictures are encoded by the picture processor 20 of FIG. 1, with the encoder 101 being locked in operation by the frame synchronization signal S2.
If the input picture S1 is free of redundant fields, the moving picture encoding system operates flawlessly by employing the frame synchronization signal S2.
However, on certain occasions redundant pictures are contained in the input picture S1.
Such redundant picture is contained in the moving picture obtained on recording e.g. a motion picture film in a VTR by photo-electric conversion. That is, the number of picture frames of the motion picture film as an original picture source is 24 per second, whereas that of the NTSC television system is 30 frames (60 fields) per second. To compensate for the six frames (12 fields) per second which fall short, the same fields are repeated at a rate of one field per two picture frames for converting the two picture frames into five fields thereby converting the 24 picture frames into 60 fields, that is 30 frames. This method is termed 3:2 pull-down, as will be explained subsequently in detail. The repeated fields are the same as the previous fields and represent redundant pictures.
With the moving picture encoding system, the data is diminished by detecting and not encoding the redundant pictures. Thus, although not shown in the example of FIG. 1, the encoder 101 detects the redundant pictures in the pre-processing process and simply omits encoding the redundant pictures.
This processing operation is shown specifically in FIG. 3.
In the present example, the redundant pictures are shown by plain textured fields and are not encoded.
If the plain-textured field is the odd field, it is the same as the immediately previous odd field, whereas, if the plain-textured field is the even field, it is the same as the immediately previous even field. Thus, one field is eliminated every five fields and a new input frame is produced by two consecutive fields next to the eliminated field.
The timing of the frame entering the next-stage picture processor is asynchronous with respect to the frame synchronization signal S2, as may be seen by a timing pulse S3, such that there is no possibility of locking operations with respect to the frame synchronization signal S2. The result is that, with the moving picture processing system of FIG. 1 employing the frame synchronization signal S2 in the picture processing system, the frame synchronization signal S2 cannot be used in e.g., the picture processor 20.
On the other hand, in case of processing not only the usual moving pictures shown in FIG. 2 but also the moving pictures including redundant pictures shown in FIG. 3. the processing by the picture processor 20 is increased in complexity depending on whether or not the pre-processing is to be performed.
In addition, with a series of moving pictures containing redundant pictures in an irregular manner, the frame timing may be changed irregularly in a more complex fashion. There is no up to now a picture processing device capable of coping with all of these variable timings, and it is difficult to produce such picture processing device.